Number of independent parameters in the Mueller matrix representation of homogeneous depolarizing media

In general the transmission of polarized light through a homogeneous depolarizing sample has motion-reversal symmetry because the response remains the same for light traveling in the opposite direction. As a consequence, the optical properties of a sample, characterized by the differential Mueller matrix, must be invariant upon motion reversal. This Letter shows that the 16 parameters of the differential Mueller matrix must therefore obey six conditions to satisfy this symmetry. This limits the number of independent parameters to 10. The 10 elementary optical properties of a depolarizing homogeneous medium are defined and discussed. (C) 2013 Optical Society of America